/* Copyright (C) 2004  All Rights Reserved.  */

/*
 * Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All rights
 * reserved.
 *
 * License to copy and use this software is granted provided that it
 * is identified as the "RSA Data Security, Inc. MD5 Message-Digest
 * Algorithm" in all material mentioning or referencing this software
 * or this function.
 *
 * License is also granted to make and use derivative works provided
 * that such works are identified as "derived from the RSA Data
 * Security, Inc. MD5 Message-Digest Algorithm" in all material
 * mentioning or referencing the derived work.
 *
 * RSA Data Security, Inc. makes no representations concerning either
 * the merchantability of this software or the suitability of this
 * software for any particular purpose. It is provided "as is"
 * without express or implied warranty of any kind.
 *
 * These notices must be retained in any copies of any part of this
 * documentation and/or software.
 *
 */

#include "pal.h"

#include "auth_md5.h"

#define S11 7
#define S12 12
#define S13 17
#define S14 22
#define S21 5
#define S22 9
#define S23 14
#define S24 20
#define S31 4
#define S32 11
#define S33 16
#define S34 23
#define S41 6
#define S42 10
#define S43 15
#define S44 21

static const u_char PADDING[64] = {
   0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/* F, G, H and I are basic MD5 functions.
 */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z)))

/* ROTATE_LEFT rotates x left n bits.
 */
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
Rotation is separate from addition to prevent recomputation.
 */
#define FF(a, b, c, d, x, s, ac) { \
 (a) += F ((b), (c), (d)) + (x) + (u_int32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define GG(a, b, c, d, x, s, ac) { \
 (a) += G ((b), (c), (d)) + (x) + (u_int32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define HH(a, b, c, d, x, s, ac) { \
 (a) += H ((b), (c), (d)) + (x) + (u_int32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }
#define II(a, b, c, d, x, s, ac) { \
 (a) += I ((b), (c), (d)) + (x) + (u_int32_t)(ac); \
 (a) = ROTATE_LEFT ((a), (s)); \
 (a) += (b); \
  }

/* Encodes input (u_int32_t) into output (u_char). Assumes len is
   a multiple of 4.  */
static void
auth_md5_encode (u_char *output, u_int32_t *input, unsigned int len)
{
   unsigned int i, j;
   
   for (i = 0, j = 0; j < len; i++, j += 4) {
      output[j] = (u_char)(input[i] & 0xff);
      output[j+1] = (u_char)((input[i] >> 8) & 0xff);
      output[j+2] = (u_char)((input[i] >> 16) & 0xff);
      output[j+3] = (u_char)((input[i] >> 24) & 0xff);
   }
}

/* Decodes input (u_char) into output (u_int32_t). Assumes len is
   a multiple of 4.  */
static void
auth_md5_decode (u_int32_t *output, u_char *input, unsigned int len)
{
   unsigned int i, j;
   
   for (i = 0, j = 0; j < len; i++, j += 4)
      output[i] = ((u_int32_t)input[j]) | (((u_int32_t)input[j+1]) << 8) |
         (((u_int32_t)input[j+2]) << 16) | (((u_int32_t)input[j+3]) << 24);
}

/* MD5 basic transformation. Transforms state based on block.  */
static void
auth_md5_transform (u_int32_t state[4], u_char block[64])
{
   u_int32_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];

   auth_md5_decode (x, block, 64);

   /* Round 1 */
   FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */
   FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */
   FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */
   FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */
   FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */
   FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */
   FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */
   FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */
   FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */
   FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */
   FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
   FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
   FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
   FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
   FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
   FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

   /* Round 2 */
   GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */
   GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */
   GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
   GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */
   GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */
   GG (d, a, b, c, x[10], S22,  0x2441453); /* 22 */
   GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
   GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */
   GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */
   GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
   GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */
   GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */
   GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
   GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */
   GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */
   GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

   /* Round 3 */
   HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */
   HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */
   HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
   HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
   HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */
   HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */
   HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */
   HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
   HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
   HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */
   HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */
   HH (b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */
   HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */
   HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
   HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
   HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

   /* Round 4 */
   II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */
   II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */
   II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
   II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */
   II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
   II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */
   II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
   II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */
   II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */
   II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
   II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */
   II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
   II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */
   II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
   II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */
   II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

   state[0] += a;
   state[1] += b;
   state[2] += c;
   state[3] += d;

   /* Zeroize sensitive information.
    */
   pal_mem_set (x, 0, sizeof (x));
}

/* MD5 initialization. Begins an MD5 operation, writing a new context.  */
void
auth_md5_init (AUTH_MD5_CTX *context)
{
   context->count[0] = context->count[1] = 0;

   /* Load magic initialization constants.
    */
   context->state[0] = 0x67452301;
   context->state[1] = 0xefcdab89;
   context->state[2] = 0x98badcfe;
   context->state[3] = 0x10325476;
}

/* MD5 block update operation. Continues an MD5 message-digest
   operation, processing another message block, and updating the
   context.  */
void
auth_md5_update (AUTH_MD5_CTX *context,
                 const void *inbuf, unsigned int inputLen)
{
   u_char *input = (u_char *)inbuf;
   unsigned int i, index, partLen;

   /* Compute number of bytes mod 64 */
   index = (unsigned int)((context->count[0] >> 3) & 0x3F);

   /* Update number of bits */
   if ( (context->count[0] += ((u_int32_t)inputLen << 3)) < ((u_int32_t)inputLen << 3))
      context->count[1]++;

   context->count[1] += ((u_int32_t)inputLen >> 29);

   partLen = 64 - index;

   /* Transform as many times as possible.
    */
   if (inputLen >= partLen)
   {
      pal_mem_cpy (&context->buffer[index], input, partLen);
      auth_md5_transform(context->state, context->buffer);

      for (i = partLen; i + 63 < inputLen; i += 64)
         auth_md5_transform(context->state, &input[i]);

      index = 0;
   }
   else
   {
      i = 0;
   }

   /* Buffer remaining input */
   pal_mem_cpy (&context->buffer[index], &input[i], inputLen-i);
}

/* MD5 finalization. Ends an MD5 message-digest operation, writing the
   the message digest and zeroizing the context.  */
void
auth_md5_final (u_char digest[16], AUTH_MD5_CTX *context)
{
   u_char bits[8];
   unsigned int index, padLen;

   /* Save number of bits */
   auth_md5_encode(bits, context->count, 8);

   /* Pad out to 56 mod 64.
    */
   index = (unsigned int)((context->count[0] >> 3) & 0x3f);
   padLen = (index < 56) ? (56 - index) : (120 - index);
   auth_md5_update(context, PADDING, padLen);

   /* Append length (before padding) */
   auth_md5_update(context, bits, 8);
   
   /* Store state in digest */
   auth_md5_encode(digest, context->state, 16);

   /* Zeroize sensitive information.
    */
   pal_mem_set (context, 0, sizeof (*context));
}

void
auth_md5_authenticator (u_char *buf)
{
  AUTH_MD5_CTX c;
  pal_clock_t secs;

  /* Something random.  */
  secs = pal_time_clock ();

  auth_md5_init (&c);
  auth_md5_update (&c, (u_char *)&secs, sizeof (pal_clock_t));
  auth_md5_final (buf, &c);
}

void
auth_hmac_md5 (u_char *text, int text_len,
               u_char *key, int key_len, u_char *digest)
{
  AUTH_MD5_CTX context;
  u_char k_ipad[65];    /* inner padding - key XORd with ipad.  */
  u_char k_opad[65];    /* outer padding - key XORd with opad.  */
  u_char tk[16];
  int i;

  /* if key is longer than 64 bytes reset it to key=MD5(key).  */
  if (key_len > 64)
    {
      AUTH_MD5_CTX      tctx;

      auth_md5_init (&tctx);
      auth_md5_update (&tctx, key, key_len);
      auth_md5_final (tk, &tctx);

      key = tk;
      key_len = 16;
    }

  /* The HMAC_MD5 transform looks like:

     MD5(K XOR opad, MD5(K XOR ipad, text))

     where K is an n byte key ipad is the byte 0x36 repeated 64 times

     opad is the byte 0x5c repeated 64 times
     and text is the data being protected.  */

  /* Start out by storing key in pads.  */
  pal_mem_set (k_ipad, 0, sizeof (k_ipad));
  pal_mem_set (k_opad, 0, sizeof (k_opad));
  pal_mem_cpy (k_ipad, key, key_len);
  pal_mem_cpy (k_opad, key, key_len);

  /* XOR key with ipad and opad values.  */
  for (i = 0; i < 64; i++)
    {
      k_ipad[i] ^= 0x36;
      k_opad[i] ^= 0x5c;
    }
  
  /* Perform inner MD5.  */
  auth_md5_init (&context);                     /* Init context for 1st pass */
  auth_md5_update (&context, k_ipad, 64);       /* Start with inner pad.  */
  auth_md5_update (&context, text, text_len);   /* Then text of datagram.  */
  auth_md5_final (digest, &context);            /* Finish up 1st pass.  */
  
  /* Perform outer MD5.  */
  auth_md5_init (&context);                     /* Init context for 2nd pass */
  auth_md5_update (&context, k_opad, 64);       /* Start with outer pad. */
  auth_md5_update (&context, digest, 16);       /* Then results of 1st hash. */
  auth_md5_final (digest, &context);            /* Finish up 2nd pass.  */
}
